It is a car with a lot of "fancy electronics". There is a memory saver that plugs into the 16 pin OBD diagnostic socket under the dash that saves computer memory. See if you can find one on line, don't confuse the device with the one that is sold that plugs into the cigarette lighter of your car as cigarette lighters are not live on many cars when the ignition key is off.
This link is a fancy one
http://www.summit-equipment-outlet.com/schumacher-obd-memory-saver.html
This link
http://www.walmart.com/ip/Schumacher-OBD-Memory-Saver-Cable/15140207?sourceid=1500000000000003260530&ci_src=14110944&ci_sku=15140207
is one that would be a cheaper alternative but needs its end modified and attached to another 12 volt battery (extend the cables put two alligator clips on it and attach it to another car battery in your driveway. plug in to connector, keys off drivers window open, doors all closed.

...ed in Melbourne, Australia, and my W8 Passat has done 142,000km. It has just had the original battery replaced, but upon replacement, the electrical system no longer functioned properly. The rear...